Piston pump with self-lubricating pistons

ABSTRACT

A pump having pistons that actuate a pumping device by suction and compression and having novel means for sealing the fluid being pumped from the lubricating fluid and for ensuring lubrication between the pistons and their cylinders. The reciprocation of the pistons is made to pump the lubricating fluid between them and the cylinder and to return the fluid to an internal lubricant reservoir. A swash plate acts also as a circulating pump for sending the lubricating fluid through an external cooling reservoir.

United States Patent 11 1 Bic kford 2 l v 1111'. 3,811,798 1451 May 21,1974

PISTON PUMP WITH SELF-LUBRICATING WATER 1 [541' 5/1972 Kitchen 417/269 S O S 2,376,856 5/1945 Hatch 417/269 3,297,106 1/1967 Hanson et al.... 184/55 A [7 Inventor: J Blckford, a ah 3,361,077 1/1968 Freeman 417/269 3,584,541 61971 C h 1 92 168 [73] Asslgnee: q systems San Rafael 3,292,554 12/1966 417/269 a 2,842,068 7/1958 Sundin., 417/269 22 filed: J 19 1972 3,191,542 6/1965 Hughes 417/269 [21] Appl' 273154 Primary Examiner-William L. Freeh Assistant Examiner-G. P. LaPointe [52] U.S. Cl. 417/269, 92/156 At rn y. Ag nt. or mn, Wickersham & [51] Int. Cl. F04b l/12, FOlb 31/10 Erickson [58] Field of Search 417/269, 270, 437; 92/80,

, .92/82, 153, 1 56, 168; 277/188 [57] ABSTRACT [56] Ref rences Cit d A pump having pistons that actuate a pumping device UNITED STATES PATENTS by suction and compression and having novel means forusealing the fluid being pumped from the lubricatxason 277/188 g fluid and for ensuring lubrication between the p enry et al.. 277/188 h h 2,963,304 12/1960 Comlossy.... 277/188 tons and their cylinders. T e rec procatlon oft e p1s- 2,405,938 8/1946 B6611 417/269 tons 18 made 10 P p the lubrlcatmg fluld between 1,546,596 7/1925 Mader 92/156 them and the cylinder andto return the fluid to an in- 2,669,185 2/1954 Tallis 417/269 ternal lubricant reservoir. A swash plate acts also as 21 0 3/1967 Wirth 92/168 circulating pump for sending the lubricating fluid 2,392,543 Mercier .L. 3 through an external cooling reservoir 3,085,514 4/1963 1 Budzich .1 417/203 2,433,222 12/1947 Huber, 417/270 21 Claims, 6 Drawing Figures WATER 4 1 OUT 53 93 as 7 as as 24 45 51 Q. m 92 73 67 9 e5 e1 82 A 66 e 50 e1 79 i 62' 1 26 1 g 13 m OUT [0 38/ '1 L35 37 20v 9 29 PATEINTEDKAY 2 i 1914 saw 1 OF 3 PATENTEDIIH 2 1 m4 SHEEIZDF3 FiG 2 'bricant through the internal reservoir and 1 WITH SELF-LUBRICATING PISTON PUMP PISTONS piston type having a novel lubrication system and a sealing system.

In previous pumps the lubrication between the pistons and their cylinders was typicaally accomplished by grease fittings, or by pressure lubrication requiring a separate'oil pump or splash oiling. In all these "cases the lubricant seals were in the cylinder, and the lubrication was marginal. Foreign particles were liable to get in past the seals and, if they got in, they caused scoring of the piston or the cylinder, leading to binding and galling of the mating surfaces. The present invention overcomes these lubrication and sealing problems.

In pumps where the lubricant seal between the piston and cylinder is in the working area, the clearance between the cylinder and the piston has to be so small that adequate lubrication is very difficultto achieve. Moreover, in high-pressure pumps where the sealing is effected between the piston and the cylinder, the cylinder tends to be. stretched by the pressure exerted on it and therefore to induce a small bypass of fluid, the amount of bypass increasing as the pressure of the pump increases. This mixes the fluid being pumped with the lubricant, to the disadvantage of both. In the present invention, the seals are located voutside this working area,

and the clearance between the piston and cylinder can therefore be large enough to insure adequate lubrication. In the pump of this invention, the sealing is done in the valve head, outside the piston-cylinder, working area. Sealing is much more effective, partly because the valve head is much stronger and less likely to'permit bypassing. v r

The structure of this invention also reduces the head space on the end of the piston, and this, in turn, reduces the shock wave that tends to produce the water hammer effect found in many high-pressure pumps.

' The same structure of the present invention makes it possible for the pump to be more compact, for the cylinder and its sleeve need not accommodate lubricant seals and can be utilized solely as bearing areas. 4

Another problem with the prior art was the difficulty of replacing the lubricant seals, and the present invention makes seal replacement simple and quick.

Another feature of the present invention is the use of the drive shaft and the swash plate mounted on it as substantially a centrifugal pump for circulating theluthrough an external reservoir and cooling system.

I SUMMARY OF THE INVENTION The invention provides a pump having a series of piston's that are reciprocated inside respective cylindrical sleeves which are themselves supported in parallel relationship in a body member inside the housing. One end of each piston and cylindrical sleeve is open to an oil reservoir inside the housing, in which the reciprocating drive mechanism for the pistons is also located. Preferably this is a swash plate mounted on a drive shaft. Each cylindrical sleeve fits snugly in the bore of the piston, and each sleeve also provides at the end remote from the oil reservoir an annular chamber. A passage outer end of that recess and the end of the annular leads from this annular chamber to a longitudinally extending groove on the exterior surface of each sleeve, which leads to the lubricant reservoir and affords a means for returning the lubricant to the reservoir.

The piston has a larger diameter portion which reciprocates in the cylindrical sleeve and a somewhat smaller diameter portion that extends through a cylindrical bore in a second body member that is spaced away from the first-named body member, with the fit there being a typical piston-cylinder fit. The shoulder at which the two piston portions meet lies inside the cylindrical bore inall of almost all positions of the piston relative to the cylinder.

The second body member has an annular recess, and a plate between the two body members closes both the chamber of the sleeve. An O-ring is provided around the narrower-diameter portion of the piston, inside the annular chamber, and it moves back and forthwith the reciprocation of the piston to open the lubricant return passageway between the cylindrical bore and the groove, or to close it, depending upon the direction of movement of the piston. A second O-ring is held in the annular chamber of the second body member, with a back-up ring in contact with the plate between the two body members; this second O-ring serves to provide a tight seal there. for the narrower-diameter portion of the piston, enabling suction to develop for actuating one of a pair of valves in the pumping chamber so that one valve is opened upon suction, while the second one is closed, and then the second one is opened by pressure while the first one is closed.

It will be explained below how the combination of the groove, the annular chamber, its O-ring, and a carefully developed tolerance in the cylindrical bore enable lubrication of the piston.

The invention also makes it possible to provide for superior circulation of lubricant in the reservoir by employing the drive shaft and its swash plate as a centrifugalpump-therein, and this same structure also circulates the lubricant externally through a cooling reservoir'and brings it back into the internal reservoir. This cant supply pump for it does not increase the internal pressure in the pump, with consequent effect on the sealing rings.

Also, the structure makes it much simpler to replace parts, assembly and disassembly being very simple, with sealing O-rings at strategic places.

Other objects and advantages of the invention will appear from the following description of a preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a view in elevation and partly in section of a pump embodying the principles of the invention. j

FIG. 2 is a fragmentary enlarged view in section of one of the pistons and its associated members, the piston being shown in one extreme position.

FIG. 3 is a view similar to FIG. 2 with the piston in its other extreme position.

FIG. 4 is a view in side elevation of the pump of FIG. 1, showing the external lubricant cooling reservoir, all on a smaller scale than in FIG. 1.

FIG. 5 is a view in end elevation of the assembly of FIG. 4.

DESCRIPTION OF A PREFERRED EMBODIMENT The pump of this invention comprises a housing 10, preferably made up of several members in order to make disassembly'easy. Thus, there may be a first cylindrical housing member 11 having a radially extending oil outlet passage 12 therethrough to which an oil conduit 13 may be connected. One end of the cylindrical housing member 11 is closed by an annular end plate 14 having a bore 15 to accommodate a rotary drive shaft 16 which extends through it and also having an oil inlet passage 17 connected to an oil conduit 18. Bolts 19 hold the members 11 and 14 together.

The other end of the cylindrical housing member 11 is closed by a first cylindrical body- 20, held to a flange.

bers can readily'be disassembled and are sealed when put together. The drive shaft 16 has a bearing 27 in a recess 28 in the end plate 14 and continues into a recess 30 where bearings 31 are provided in the body member 20. An-O-ring seal 32 in the end plate 14 prevents leakage around the shaft 16.

A second cylindrical housing member 35 is bolted to the first body 20 by bolts 33 and sealed to it by an O- ring 36, and is provided at its lower end with a drain opening 37 to drain out any excess lubricant or bypassed pump fluid. The housing member 35 also has an inlet passage 38 for the fluid being pumped, which may be water or some other liquid coming from a conduit 39. Inside the member 35 is mounted a second body or valve head 40. The second body or valve head 40 is spaced from the first body 20 by an annular spacing disk 41 having a series of round openings 42, and 0- rings 43 and 44 are provided to seal between the members 3S and 40. The second body 40 provides a series of stepped receptacles 45, each receiving fluid from a manifold 46 that lies between the members 35 and 40, and the second body 40 provides a water-outlet passage 47 collecting fluid from a series of outlets 48 leading from the receptacles 45.

In each receptacle are inserts providing cages for a double valve pump valve mechanism. Ball valves are shown in FIG. 1 and cone valves are shown in FIG. 6; the basic structure is the use of two check valves, one opening on suction, the other opening on pressure. In FIG. 1, a first ball 50 is urged by a spring 51 to close an inlet opening 52 and opens when suction pulls the ball 50 up against the pressure of the spring 51. A second ball 53 is urged by a spring 54 against an opening 55 and opens when the fluid between the balls 50 and 53 is placed under pressure. The fluid pumped may be water, hot or cold, or other liquids, including refrigerants.

The first body 20 is provided with a series of cylindrical bores 57, which may be stepped at a shoulder 58 to provide a smaller-diameter bore portion 59, and in these bores 57 is inserted a cylindrical sleeve 60, which.

acts as the cylinder of the device. There are a series of sleeves 60 around the device for instance, there may 20 and the cylindrical sleeve 60. The sleeve 60 has a cylindrical bore 64 extending from a first end 65, lying inside the reservoir 21 to a second end where there is an annular chamber 67 having a shoulder 68. A passage 69 leads to an axially extending groove 70 in the exterior wall of the sleeve 60 and extends longitudinally from the outer end of the passage 69 to the shoulder 61, where a short radial groove 71 opposite the shoulder 58 leads to an axially extending groove 72 that empties into the reservoir 21. In the annular chamber 67 is a very important O-ring 73 that will be discussed later.

Each cylinder 60 has a corresponding piston 75, and each piston 75 has two different diameter portions meeting at a shoulder 76: a wider-diameter portion 77 reciprocates inside the cylindrical bore 64 and a narrower-diameter portion 78 reciprocates inside a bore 80 in the second body 40. Each piston 75 has a first end 81 in the reservoir 21, with a shoulder 79 thereon, and a second end 82 adjacent the ball valve mechanism. The end 81 adjoins a ball 83 for swiveling a thrust bearing 84 which faces the face bearings 24 of the swash plate 22. A pair of spring retainers 85 and 86 are provided for a spring 87; one of the retainers 85 is mounted against the shoulder 79 of the piston 75, and the other retainer 86 is supported around the sleeve 60 and against the face of the first body 20. The spring 87 holds the thrust bearing 84 at all times in firm engagement with the swash plate thrust bearings 24.

While a swash plate construction has been shown, the invention is operable with other means for driving the pistons, and any number of pistons may be spaced radially around the actuating shaft for axial movement parallel to the axis of the drive shaft.

The second body 40 has an annular recess 90 in which there is a sealing ring 91 which seals between the second body member 40 and the smaller-diameter portion 78 of the piston 75, and there is a back-up ring 92 for the sealing ring 91. The back-up ring 92 abuts an annular member 93 and may fit either in a groove 94 therein or against the face. Each member 93 is supported by the spacing disk 41 in one of the openings 42, in which it fits loosely..The members 93 are thicker than the disk 41, to provide pressure and to prevent extrusion of the rings 91, 92 and 73, the members 93 being held in compression between the members 20 and 40. A drain passage 95 may be provided as a recess in the member 20. The member 93 serves both to close the end of the annular recess 90 and to close the end of the annular recess 67.

The clearance between the narrower-diameter piston portion 78 and the bearing member 93 is minimal to prevent any extrusion of the back-up ring 92. The back-up ring 92 is made of material that is not subject to cold flow and can provide a zero clearance, so that the sealing ring 91 can make a substantially perfect seal with the reciprocating shaft portion 78. This back-up ring 92 is preferably made of a combination of fiberglass, bronze, and Teflon (tetrafluoroethylene). For example, one suitable ring 92 is made up of 17 percent fiberglass, 40 percent bronze, and 43 percent Teflon. Composition may vary, depending on the material being pumped and on the temperature, but the back-up ring 92 should have good resistance to wear and to the lubricant and to the fluid beingpumped. The sealing ring 91 is preferably a high-pressure seal quad ring, but it may be an O-ring or packing depending upon the type needed for the fluid and pressure being pumped. The portion of the sealing ring 91 that is exposed to pressure is kept minimal, and this helps to reduce the grippingpressure 'or squeeze, so that the life of the sealing ring 91 is extended. The features just'described are adaptable to other types of pumps or motors, including various configurations and are not limited to axial pistonpumps. The sealing'ring seal 91 isolates the highpressure area from the atmosphere and from the drive end and the sealing rings 63, 73, and 91 cooperate to seal the lubrication area from the pumping area.

The piston portion 78 is preferably about 0.010 inch smaller in diameter. than the piston portion 77. The difference can be somewhat greater or somewhat smaller if desired, but this is a preferable figure. The piston portion 77 fits in the bore 64 with a clearance of about 0.0015 inch to 0.0025 inch, so that lubricant can readily flow in between them. r

The O-ring 73 has minimal squeeze in the annular chamber 67 of the sleeve 60, but fits. in a-normal way on the piston portion 78, so that the O-ring 73 can move in-the annular chamber 67 and function as a valve, opening and closing the port of the passage 69. On the outward portion of the cycle, that is, as the piston 75 moves to the right in FIGS. 1-3 (in other words,

when the piston is moving away from the valve pumping mechanism and toward the swash plate 22) the piston 75 draws the O-ring 73 against the shoulder 68 and thereby closes the passageway 69, sothat there is no movement of oil through the cylindrical bore 64 or through the groove 70 during this time. This movement also means that the smaller-diameter portion 78 of the piston 75 enters deeper within the cylindrical bore 64, and as a result increases the total volume of the space between the. cylindrical bore 64 and the piston 75. Thus, this space ismuch larger in FIG. 3 than in FIG.

2, and with the increase in capacity, the pressure is reduced and oil is drawn in along the piston portion 77, moving oppositely to the direction in which the piston 75 is moving,- and passes into the clearance between the largerdiameter piston portion 77 and the bore 64 and .there flows to the clearance betweenthe smallerdiameter piston portion 78 and the bore 64. p

. When the piston 75 moves in the opposite direction (to the left in FIGS. 1-3, in other .words, towards the ball valves and away from the reservoir 21) the total clearance volume between the piston 75 and the bore 64 is, of course, reduced in size, and therefore pressure builds up. This pressure, together with the movement of the piston 75, moves the O-ring 73 away from the shoulder 68, exposing the passage or port 69 so that oil then is urged by this buildup of pressure to flow from the annular chamber 67 and from the cylindrical bore 64 into the groove 70. It moves then through the grooves 70, 71, and 72 to the reservoir 21, completing the cycle of oil movement in the circulating pattern. Thus there is an intermittent but regular flow of oil between the piston 75 and the cylinderbore 64, moving in one direction inwardly and then moving by the groove back to the reservoir 21, so that lubrication is always assured. The reservoir 21 is of course flood lubricated and is always kept full of oil.

It should be noted that the close fitting surfaces 78 and 93 are short in length, and sufficient oil is carried on the piston surface 78 to keep this mating surface lubricated, the seal here being provided by the sealing ring 91 and its back-up ring 92.

The O-rings 25, 26, 36, 43, and 44 provide a sealing structure enabling one to take the pump apart and reassemble it readily, when the bolts 19, 29 and 33 are removed. Thus, once the bolts 33 are removed, the valve head or body 40 and the member 35.can be removed from the body 20 and the disk 41 then removed; when the bolts 19 are removed, the end plate 14 comes off, readily; and. when the bolts 29 are removed, then the cylindrical portion 11 can be removed from the first body 20.-When the first body 20 and the second annular housingmember 35 along'with the valvehead 40, are detached from each other, this gives adequate access for replacing the piston seals 73 and 91, for example, withoutdisassembling the piston sleeves 60 from their body 20, and this can be done without separating the body 20 from the member 11, letting the pistonswash plate assembly remain in place.

In this pump, the oil reservoir 21 should be kept on about the same level as the drive case. By feeding the oil to the case via the inlet 17 at about the center of the housing 10 and by draining or discharging it via the outlet 12 on the outer periphery of the housing 10, the rotation of thedrive shaft 16 helps to circulate the lubricant, acting substantially as a centrifugal pump. An air bleed valve 96 frees the lubricant from air.

The oil circulation system is best understood with reference to FIGS. 4 and 5 as well as FIG. 1. An external oil reservoir 100 is connected to the housing 10 by the conduits 13 and 18. The reservoir 100 has fins 101 for cooling. The oil from the reservoir 100 flows via the conduit 13 to the inletconduit 17 where it approaches the center of the housing 10, near the drive shaft 16. It flows through the'bearings 27, lubricating them, into the reservoir 21. There, the rotation of the shaft 16 and the rotation of the eccentric swash plate 22 move the oil radially outwardly toward the pistons 75, which, as already described in detail use it for self-lubrication. The outlet 12 conducts the oil to the conduit 13 and thence to the cooler-reservoir 100, the circulation being achieved by the shaft 16 and swash plate 22 without any external pump. This is far preferable, because an external pump creates internal pressures that tend to hold the O-ring 73 in its open position at all times.

The clearances provided by this invention make it possible, in connection with the cooler-reservoir 100,

- to pump fluid over a wide variety of temperatures, de-

pending on the mechanical strength and corrosion- -resistance of the pump elements and to do this without the complicated temperature controls necessitated by other. high-pressure pumps. The cooler 100 prevents the lubricant from becoming overheated and thereby the lubricant keepsthe piston temperatures in the desired range.

' It has been stated that the suction-pressure actuation need not rely'on ball valves, as shown in FIG. 1. One alternative structure forthe suction-pressure checkvalve assembly is shown in FIG. 6. Here a tubular valve housing 110 has an inlet 111 at its lower end and has O-rings 112 and 113 for sealing the housing 110 in a drilled passage 45 in the body or valve head 40. The upper end has a spider 114 providing outlets 115.

The inlet 111 leads to a conical seat 116 and an enlarged passage 117. A spider 118 with passages 119 supports a valve member 120. The valve member 120 has a conical head 121 and a stem 122. A tubular sleeve 123 integral with the spider 118 guides the sleeve 122, and a spring 124 seated at one end against the spider 118 bears against the fiat upperend 125 of the valve member 120 to urge the head 121 towards its seat 116. An opening 126 provides communication be tween the passage 117 and the base 80 in the member 40, for alternate application of suction and pressure to the fluid being pumped.

The passage 117 leads to a narrower passage 127 and thence to a seat 128 for a second valve 130 like the valve 120. Both valves 120 and 130 may have an O-ring 131 in their conical heads for better seating. It is apparent that the valve 120 is seated by pressure and opened by suction, accordingto the direction of movement of the piston 75. Similarly, the valve 130 is closed by suction and seated by pressure. This operation is as previously described.

To those skilled in the art to which this invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

1 claim:

1. in a pumping mechanism having a housing, an in ternal oil reservoir therein filled with lubricant, at least one reciprocating piston in a stationary cylindrical bore, and means in said reservoir for reciprocating said piston, the combination comprising:

said cylindrical bore having a first end in said reservoir, a first portion extending to an annular chamber meeting said cylindrical bore at a shoulder, with a longitudinally extending passage extending outside said bore adjacent to said shoulder to said first end, and a'second smaller-diameter portion beyond said annular chamber terminating at a second end,

said piston having a first end in said reservoir and afirst portion having a diameter-just enough smaller than said first portion of said cylindrical bore to enable passage of oil therebetween during reciprocation, said piston having a second end beyond said annular chamber and within saidsecond bore portion at all times and a second portion smaller in diameter than said first piston portion extending from said second piston end and meeting said first piston portion at a rim always lying within said first portion of said cylindrical bore,

an O-ring in said annular chamber and movable against and away from said shoulder and in sealing of said second portion of said piston in said second bore portion,

said sealing means sealing off the fluid being pumped from said lubricant, while said O-ring acts as a valve opening and closing the passage between said groove and said cylindrical bore as the piston reciprocates, thereby lubricating said cylindrical bore and said piston.

2. The combination of claim 1 wherein said second piston portion is about 0.010 inch smaller in diameter than said first piston portion.

3. The combination of claim 2 wherein said diameter of said first piston portion is about 0.0015 to 0.0025 inch less than that of said cylindrical bore.

4. The combination of claim 1 wherein there is an enlarged annular recess in said second bore portion and said sealing means comprises an elastomeric sealing ring in said annular recess and a back-up ring in said annular recess between said sealing ring and said bearing member. 5. In a pumping mechanism having a housing, an oil I reservoir therein filled with lubricant, at least one rerelation with said second portion of said piston, Y

thereby having a position closing said passage and a position opening said passage, sealing means sealing between said second bore portion and said second portion of said piston, and, pumping mechanism in said housing beyond said second end of said piston and actuated by the suction ciprocating piston in a stationary cylindrical bore, means in said reservoir for reciprocating said piston, the combination comprising:

an enlarged annular recess in said bore,

an elastomeric sealing ring of circular cross-section in said annular recess sealing between said bore and said piston and having a crosssectional diameter slightly larger than the radial width of said recess,

a non-elastomeric back-up ring in said annular recess next to said sealing ring having substantially the same crosssection radial width as said recess, said recess being longer in its axial extent than the combined axial extent of said backup ring and said cross-sectional diameter of said sealing ring, said two rings being the only members in said recess, said back-up ring being a combination of glass fibers, bronze, and tetrafluoroethylene, each ingrei ntbs nsaressatia an, a o nt 9f? least 1 P cent ofthe total, and

pumping mechanism in said housing beyond said piston and communicating with said bore and actuated by the alternating suction and pressure provided by reciprocation of said piston,

said sealing ring sealing off the fluid being pumped from said lubricant.

6. In a pumping mechanism having a housing, an internal oil reservoir therein filled with lubricant, a plurality of reciprocating pistons each in a stationary cylindrical bore, and means in said reservoir for reciprocating said piston, the combination comprising:

a first body in said housing with one end forming a wall of said reservoir and having a bore for each cylinder,

a sleeve member fitting snugly in each said bore and providing said cylindrical bore, said sleeve having a first end in said reservoir and a second end distant therefrom having an annular chamber meeting said cylindrical bore at a shoulder, said sleeve having an exterior longitudinally extending groove extending from near said shoulder to said first end and having a bored passage connecting said groove to said annular chamber adjacent said shoulder,

. 9 each said piston having a first end insaid reservoir and a first portion having a diameter just enough smaller than said cylindrical bore to enable passage of oil therebetween during reciprocation, said piston having a second end beyond said second end of said sleeve memberat all times and a second portion smaller in diameter than said first portion extending from said second end and meeting said first portion at a rim always lying within said cylindrical bore,

a second body spaced from said first body having a bore in which said second piston portion reciprocates,

an annular bearing member between said first and second bodies and closing said annular chamber,

an O-ring in said annular chamber andmovable be.

tween said shoulder and said bearing member and sealing between said second portion of said piston and said sleeve and having a position closing the passage between said chamber and said groove and a position opening that passage, sealing means sealing between said second body and said second portion of said piston, and, pumping mechanism in said second body and actuated by the alternate suction and pressure provided by said second portion of said piston in said second body, said sealing means sealing off the fluid being pumped from said lubricant, while said ,O-ring acts as a valve opening and closing the passage between said groove and said cylindrical bore as the piston reciprocates, thereby lubricating said cylindrical bore and said piston. 7. The combination of claim 6 wherein said second piston portion is about 0.010 inch smaller in diameter than said first piston portion.

8. The combination of claim 7 wherein said diameter of said first piston portion is about 0.0015 to 0.0025.

inch less than that of said cylindrical bore.

9. The combination of claim 6 wherein said second body has an enlarged annular recess facing said annular bearing member and said sealing means comprises an elastomeric sealing ring in said annular recess and a back-up ring in said annular recess between said sealing ring and said bearing member. 10. The combination of claim 9 wherein said annular recess extends into a recessed portion of said bearing member.

11. The combination of claim 6 having an annular disk between said first and second body members slightly thinner than said bearing member and having the periphery thereof and connected to said external reservoir by an outlet conduit,

the rotation of said drive shaft and its swash plate in said internal reservoir circulating oil from said inlet means to said outlet means and through said external reservoir to said inlet means. 13. The combination of claim 6 wherein said housing comprises a cylindrical reservoir-containing portion closed at one end and bolted at its other end'to said first 16. In a pumping mechanism having a housing, an oil reservoir therein filled with lubricant, a plurality of reciprocating pistons each in a stationary cylindrical bore, means in said reservoir for reciprocating said piston, the combination comprising:

a first body in said housing with one end forming a wall of said reservoir and having a first bore for each cylinder, each said first bore havinga first end facing said reservoir and a second end distant therefrom, a

each said piston having a first end in said reservoir and a first portion having a diameter just enough smaller than said cylindrical bore to enable passage of oil therebetween during reciprocation, said piston-having a second end beyond said second end of said'first bore at all times and a second portion.

smaller in diameter than said first portion extending from said second end and meeting said first portion at a rim always lying within said cylindrical bore,

a second body spaced from said first body having a second bore in which said second piston portion reciprocatesand having an enlarged annular recess,

an annular bearing member between said first and second bodies and closing said annular recess,

a sealing ringof circular-cross-section in said annular recess sealing between said second'body and said second portion of said piston, and having a crosssectional diameter slightly larger than the radial width of said recess, a back-up ring in said annular recess between said sealing ring and. said bearing member, said back-up ring having substantially the same cross-sectional radial width as said recess, said recess being longer in its axial extent than the combined axial extent of said back-up ring and said crosssectional diameter of said sealing ring, said tworings being the only members in said recess, and

pumping mechanism in said second bodyand actuated by the suction of said second portion of said piston in said second body,

said sealing ring sealing off the fluid being pumped from said lubricant. v

17. The combination of claim 16 wherein said sealing ring is elastomeric and said back-up ring is nonelastomeric.

18. The combination of claim 17 wherein said backup ring is a combination of glass fibers, bronze, and tetrafluoroethylene.

19. The combination of claim 16 having an annular disk thinner than said bearing means between said first and second body members and having openings therein for holding each said bearing means loosely.

20. The combination of claim 16 having a plurality of sleeve members each fitting snugly in one said first bore and providing a said cylindrical bore, said sleeve having a first end in said reservoir and a second end distant therefrom having an annular chamber meeting said cylindrical bore at a shoulder, said sleeve having an exterior longitudinally extending groove extending from near said shoulder to said first end and having a bored passage connecting said groove to said annular chamber adjacent said shoulder, and means for closing said bored passage when said piston moves in one direction and opening it when said piston moves in the opposite direction.

21. In a pumping mechanism having a housing, an oil reservoir therein filled with lubricant, a plurality of reciprocating pistons each in a stationary cylindrical bore, means in said reservoir for reciprocating said piston, the combination comprising:

a first body in said housing with one end forming a wall of said reservoir and having a first bore for each cylinder, each said first bore having a first end facing said reservoir and a second end distant therefrom,

each said piston having a first end in said reservoir and a first portion having a diameter just enough smaller-than said cylindrical bore to enable passage of oil therebetween during reciprocation, said piston having a second end beyond said second end of a second body spaced from said first body having a second bore in which said second piston portion reciprocates and having an enlarged annular recess,

an annular bearing member between said first and second bodies and closing said annular recess,

a sealing ring in said annular recess sealing between said second body and said second portion of said piston,

a back-up ring in said annular recess between said sealing ring and said bearing member,

pumping mechanism in said second body and actuated by the suction of said second portion of said I piston in said second body,

said sealing ring sealing off the fluid being pumped from said lubricant,

a plurality of sleeve members each fitting snugly in one said first bore providing a said cylindrical bore, said sleeve having a first end in said reservoir and a second end distant therefrom having an annular chamber meeting said cylindrical bore at a shoulder, said sleeve having an exterior longitudinally extending groove extending from near said shoulder to said first end and having a bored passage connecting said groove to said annular chamber adjacent said shoulder,

means for closing said bored passage when said piston moves in one direction and opening it when said piston moves in the opposite direction,

an O-ring in said annular chamber movable between said shoulder and said spacing member and sealing between said second portion of said piston and said sleeve and having a position closing the passage between said chamber and said groove and a position opening that passage,

said O-ring acting as a valve opening and closing the passage between said groove and said cylindrical bore as the piston reciprocates, thereby lubricating said cylindrical bore and said piston. 

1. In a pumping mechanism having a housing, an internal oil reservoir therein filled with lubricant, at least one reciprocating piston in a stationary cylindrical bore, and means in said reservoir for reciprocAting said piston, the combination comprising: said cylindrical bore having a first end in said reservoir, a first portion extending to an annular chamber meeting said cylindrical bore at a shoulder, with a longitudinally extending passage extending outside said bore adjacent to said shoulder to said first end, and a second smaller-diameter portion beyond said annular chamber terminating at a second end, said piston having a first end in said reservoir and a first portion having a diameter just enough smaller than said first portion of said cylindrical bore to enable passage of oil therebetween during reciprocation, said piston having a second end beyond said annular chamber and within said second bore portion at all times and a second portion smaller in diameter than said first piston portion extending from said second piston end and meeting said first piston portion at a rim always lying within said first portion of said cylindrical bore, an O-ring in said annular chamber and movable against and away from said shoulder and in sealing relation with said second portion of said piston, thereby having a position closing said passage and a position opening said passage, sealing means sealing between said second bore portion and said second portion of said piston, and, pumping mechanism in said housing beyond said second end of said piston and actuated by the suction of said second portion of said piston in said second bore portion, said sealing means sealing off the fluid being pumped from said lubricant, while said O-ring acts as a valve opening and closing the passage between said groove and said cylindrical bore as the piston reciprocates, thereby lubricating said cylindrical bore and said piston.
 2. The combination of claim 1 wherein said second piston portion is about 0.010 inch smaller in diameter than said first piston portion.
 3. The combination of claim 2 wherein said diameter of said first piston portion is about 0.0015 to 0.0025 inch less than that of said cylindrical bore.
 4. The combination of claim 1 wherein there is an enlarged annular recess in said second bore portion and said sealing means comprises an elastomeric sealing ring in said annular recess and a back-up ring in said annular recess between said sealing ring and said bearing member.
 5. In a pumping mechanism having a housing, an oil reservoir therein filled with lubricant, at least one reciprocating piston in a stationary cylindrical bore, means in said reservoir for reciprocating said piston, the combination comprising: an enlarged annular recess in said bore, an elastomeric sealing ring of circular cross-section in said annular recess sealing between said bore and said piston and having a cross-sectional diameter slightly larger than the radial width of said recess, a non-elastomeric back-up ring in said annular recess next to said sealing ring having substantially the same crosssection radial width as said recess, said recess being longer in its axial extent than the combined axial extent of said backup ring and said cross-sectional diameter of said sealing ring, said two rings being the only members in said recess, said back-up ring being a combination of glass fibers, bronze, and tetrafluoroethylene, each ingredient being present in an amount of at least 15 percent of the total, and pumping mechanism in said housing beyond said piston and communicating with said bore and actuated by the alternating suction and pressure provided by reciprocation of said piston, said sealing ring sealing off the fluid being pumped from said lubricant.
 6. In a pumping mechanism having a housing, an internal oil reservoir therein filled with lubricant, a plurality of reciprocating pistons each in a stationary cylindrical bore, and means in said reservoir for reciprocating said piston, the combination comprising: a first body in said housing with one end forming a wall of said reservoir and having a bore for each cylindeR, a sleeve member fitting snugly in each said bore and providing said cylindrical bore, said sleeve having a first end in said reservoir and a second end distant therefrom having an annular chamber meeting said cylindrical bore at a shoulder, said sleeve having an exterior longitudinally extending groove extending from near said shoulder to said first end and having a bored passage connecting said groove to said annular chamber adjacent said shoulder, each said piston having a first end in said reservoir and a first portion having a diameter just enough smaller than said cylindrical bore to enable passage of oil therebetween during reciprocation, said piston having a second end beyond said second end of said sleeve member at all times and a second portion smaller in diameter than said first portion extending from said second end and meeting said first portion at a rim always lying within said cylindrical bore, a second body spaced from said first body having a bore in which said second piston portion reciprocates, an annular bearing member between said first and second bodies and closing said annular chamber, an O-ring in said annular chamber and movable between said shoulder and said bearing member and sealing between said second portion of said piston and said sleeve and having a position closing the passage between said chamber and said groove and a position opening that passage, sealing means sealing between said second body and said second portion of said piston, and, pumping mechanism in said second body and actuated by the alternate suction and pressure provided by said second portion of said piston in said second body, said sealing means sealing off the fluid being pumped from said lubricant, while said O-ring acts as a valve opening and closing the passage between said groove and said cylindrical bore as the piston reciprocates, thereby lubricating said cylindrical bore and said piston.
 7. The combination of claim 6 wherein said second piston portion is about 0.010 inch smaller in diameter than said first piston portion.
 8. The combination of claim 7 wherein said diameter of said first piston portion is about 0.0015 to 0.0025 inch less than that of said cylindrical bore.
 9. The combination of claim 6 wherein said second body has an enlarged annular recess facing said annular bearing member and said sealing means comprises an elastomeric sealing ring in said annular recess and a back-up ring in said annular recess between said sealing ring and said bearing member.
 10. The combination of claim 9 wherein said annular recess extends into a recessed portion of said bearing member.
 11. The combination of claim 6 having an annular disk between said first and second body members slightly thinner than said bearing member and having a through opening for loosely receiving said bearing member.
 12. The combination of claim 6 wherein said pumping mechanism comprises a drive shaft having a swash plate theron in said internal reservoir engaging said pistons for reciprocation thereof, an external oil-cooling reservoir, inlet means for said oil into said internal reservoir near the axial center thereof adjacent to said drive shaft and connected to said external reservoir by an inlet conduit, and outlet means for said oil from said reservoir adjacent the periphery thereof and connected to said external reservoir by an outlet conduit, the rotation of said drive shaft and its swash plate in said internal reservoir circulating oil from said inlet means to said outlet means and through said external reservoir to said inlet means.
 13. The combination of claim 6 wherein said housing comprises a cylindrical reservoir-containing portion closed at one end and bolted at its other end to said first body for ready disassembly and reassembly.
 14. The combination of claim 13 wherein said closed end of said reservoir portion is bolted thereon for easy removal.
 15. The combinaTion of claim 13 wherein said first and second body members are bolted together for easy disassembly and reassembly.
 16. In a pumping mechanism having a housing, an oil reservoir therein filled with lubricant, a plurality of reciprocating pistons each in a stationary cylindrical bore, means in said reservoir for reciprocating said piston, the combination comprising: a first body in said housing with one end forming a wall of said reservoir and having a first bore for each cylinder, each said first bore having a first end facing said reservoir and a second end distant therefrom, each said piston having a first end in said reservoir and a first portion having a diameter just enough smaller than said cylindrical bore to enable passage of oil therebetween during reciprocation, said piston having a second end beyond said second end of said first bore at all times and a second portion smaller in diameter than said first portion extending from said second end and meeting said first portion at a rim always lying within said cylindrical bore, a second body spaced from said first body having a second bore in which said second piston portion reciprocates and having an enlarged annular recess, an annular bearing member between said first and second bodies and closing said annular recess, a sealing ring of circular cross-section in said annular recess sealing between said second body and said second portion of said piston, and having a cross-sectional diameter slightly larger than the radial width of said recess, a back-up ring in said annular recess between said sealing ring and said bearing member, said back-up ring having substantially the same cross-sectional radial width as said recess, said recess being longer in its axial extent than the combined axial extent of said back-up ring and said crosssectional diameter of said sealing ring, said two rings being the only members in said recess, and pumping mechanism in said second body and actuated by the suction of said second portion of said piston in said second body, said sealing ring sealing off the fluid being pumped from said lubricant.
 17. The combination of claim 16 wherein said sealing ring is elastomeric and said back-up ring is non-elastomeric.
 18. The combination of claim 17 wherein said back-up ring is a combination of glass fibers, bronze, and tetrafluoroethylene.
 19. The combination of claim 16 having an annular disk thinner than said bearing means between said first and second body members and having openings therein for holding each said bearing means loosely.
 20. The combination of claim 16 having a plurality of sleeve members each fitting snugly in one said first bore and providing a said cylindrical bore, said sleeve having a first end in said reservoir and a second end distant therefrom having an annular chamber meeting said cylindrical bore at a shoulder, said sleeve having an exterior longitudinally extending groove extending from near said shoulder to said first end and having a bored passage connecting said groove to said annular chamber adjacent said shoulder, and means for closing said bored passage when said piston moves in one direction and opening it when said piston moves in the opposite direction.
 21. In a pumping mechanism having a housing, an oil reservoir therein filled with lubricant, a plurality of reciprocating pistons each in a stationary cylindrical bore, means in said reservoir for reciprocating said piston, the combination comprising: a first body in said housing with one end forming a wall of said reservoir and having a first bore for each cylinder, each said first bore having a first end facing said reservoir and a second end distant therefrom, each said piston having a first end in said reservoir and a first portion having a diameter just enough smaller than said cylindrical bore to enable passage of oil therebetween during reciprocation, said piston having a second end beyond said second end of said first bore at all times and a secOnd portion smaller in diameter than said first portion extending from said second end and meeting said first portion at a rim always lying within said cylindrical bore, a second body spaced from said first body having a second bore in which said second piston portion reciprocates and having an enlarged annular recess, an annular bearing member between said first and second bodies and closing said annular recess, a sealing ring in said annular recess sealing between said second body and said second portion of said piston, a back-up ring in said annular recess between said sealing ring and said bearing member, pumping mechanism in said second body and actuated by the suction of said second portion of said piston in said second body, said sealing ring sealing off the fluid being pumped from said lubricant, a plurality of sleeve members each fitting snugly in one said first bore providing a said cylindrical bore, said sleeve having a first end in said reservoir and a second end distant therefrom having an annular chamber meeting said cylindrical bore at a shoulder, said sleeve having an exterior longitudinally extending groove extending from near said shoulder to said first end and having a bored passage connecting said groove to said annular chamber adjacent said shoulder, means for closing said bored passage when said piston moves in one direction and opening it when said piston moves in the opposite direction, an O-ring in said annular chamber movable between said shoulder and said spacing member and sealing between said second portion of said piston and said sleeve and having a position closing the passage between said chamber and said groove and a position opening that passage, said O-ring acting as a valve opening and closing the passage between said groove and said cylindrical bore as the piston reciprocates, thereby lubricating said cylindrical bore and said piston. 